Seth Moulton

Representative Seth Moulton’s primary challenge to Massachusetts Senator Ed Markey hasn’t attracted as much national attention as the Democratic firefights over Senate nominations in Maine and Michigan. But the Massachusetts contest will also offer important clues about where Democrats go next — particularly whether they can honestly confront their greatest electoral challenges.

On paper, the Massachusetts showdown presents the same ideological contrast as the party’s other left-versus-center face-offs. Following Moulton’s election to the House in 2014, he’s often questioned the party’s liberal orthodoxies, while Markey has been a liberal stalwart since the mid-1970s.